Because stable electric power is required for operation of all kinds of computer systems a power supply is needed to provide the stable power to meet this end. Most power supplies are connected to an input source to get input power and have a power conversion unit to convert the input power into a driving power sent to a load. Such a conventional structure often relies on the commercial power as the power input source. In the event that the commercial power cannot provide normally, the computer systems would be shut down, or the power supply driving the computer systems could be damaged due to overload of a boost unit. To prevent the problem caused by malfunction of a single input source, a conventional approach adopts an Uninterrupted Power System (UPS) connected to the power supply. In the event that the input source malfunctions, stable power still can be temporarily provided to drive the computer systems to reduce the risk of abrupt loss of the input power.
The computer systems supported by the aforesaid UPS power supply, such as the conventional computer systems, often comprise complex and precise electronic elements. To make sure that when the computer systems are started the internal power supplies thereof can provide sufficient power for all the electronic elements, the motherboard of each computer system outputs a power supply-on (PS-ON) signal to the power supply. When the power supply can output a stable voltage, it feeds back a power good signal (PGS) to the motherboard to facilitate downstream hardware inspection process, such as power-on self-test (POST). In the event that the power supply cannot provide a normal working voltage to the computer system, no PGS is sent to the motherboard, and the computer system cannot be started normally.
Output of the aforesaid PGS relies on the power supply to output the normal working voltage. However, in the event that the commercial power is not available, the motherboard still cannot receive the PGS to perform the normal booting procedure, and the UPS equipped in the computer system cannot function as desired.